A number of devices are required to identify and discriminate between coins or other small discrete objects. Examples of these devices include coin counting or handling devices, vending machines, gaming devices such as slot machines, bus or subway coin or token fare boxes, and telephones. These devices use sensors to provide information that is used to discriminate between coins and non-coin objects. Also, the sensors are used to discriminate among different coin denominations and among coins of different countries.
Examples of coin handling devices and sensors are provided in U.S. Pat. Nos. 5,988,348 and 6,196,371. Coins, in these devices, are cleaned and collected by a coin pickup assembly. Following cleaning, the coins pass a coin sensor. The sensor provides an oscillating electromagnetic field generated on a single sensing core. The oscillating electromagnetic field, composed of one or more frequency components, interacts with the passing coin. The interactions are monitored and used to simultaneously obtain data relating to two or more parameters of a coin or other object. This data is used to classify the coin according to its physical properties, like size, core material, and cladding material. Objects recognized as acceptable coins, using the sensor data, are accepted into coin bins.
Typical coin handling devices and the associated sensors, however, can at times suffer from a number of deficiencies, including occasional discrimination errors. One major source of these discrimination errors has been temperature sensitivities associated with the sensor electronics. For example, the frequency components of the sensor magnetic field or oscillator are phase-locked to a common reference frequency. The oscillator frequency control voltage can drift as a result of temperature fluctuations in the oscillator electronics, thereby causing a drift of the reference output signal. As a large portion of the dynamic range of the typical sensor circuitry is used in accomodating the oscillator frequency control voltage drifts, less dynamic range is available for object discrimination. Therefore, the temperature fluctuations can ultimately result in a corresponding increase in discrimination errors and false-reject rates. Because some of these coin counting or handling devices are in outdoor areas where the temperature environment cannot easily be controlled, another solution is necessary.
In the drawings, the same reference numbers identify identical or substantially similar elements or acts. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the Figure number in which that element is first introduced (e.g., element 304 is first introduced and discussed with respect to FIG. 3).
Figure numbers followed by the letters “A,” “B,” “C,” etc. indicate that two or more Figures together form a complete Figure (e.g., FIGS. 3A, 3B, and 3C together form a single, complete FIG. 3), but are split between two or more Figures because of paper size restrictions.
As is conventional in the field of electrical circuit representation, sizes of electrical components are not drawn to scale, and various components can be enlarged or reduced to improve drawing legibility. Component details have been abstracted in the Figures to exclude details such as position of components and certain precise connections between such components when such details are unnecessary to the invention.
The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed invention.